Unable to attach contacts & mails

Hi,
In ZD when ever I try to attach a mail or contact to an email under the "Add Attachment" tab, I get an error. I always get a message "Clear or upload attachments before chaining tabs" and thus I am unable to navigate to either of them. Can someone please help me on how to resolve this issue?
Regards
RJ

In ZD when ever I try to attach a mail or contact to an email under the "Add Attachment" tab, I get an error. I always get a message "Clear or upload attachments before chaining tabs" and thus I am unable to navigate to either of them. Can someone please help me on how to resolve this issue?

How about giving details of the exact version of ZD that you have installed?